When high concentrations of an acidic component, such as CO2, H2S, HF, HCl, H2SO4, or H3NO3 are present in a gas, the gas is generally referred to as an “acid gas.” The acidic component of acid gas will generally cause the pH of liquids contained in the gas, such as water, to fall to between about 3 pH and about 5 pH, for example. In gas compression technology, liquids (e.g., water) that are present in the gas have been shown to cause various types of corrosion to the metal and alloy components of gas compression equipment. Such corrosion may include general corrosion, Sulfide Stress Cracking (SSC), and undeposit corrosion.
If gases containing an acidic component are compressed with aqueous water (moisture) present in the system, the resulting moisture, containing the acidic gases, may be corrosive to the internal metal components in the compressor. Condensation that forms when cooling an acidic gas may also be corrosive to the internal metal components. The corrosion is typically more severe during the initial stages of compression, because liquid water is most likely to be present during the initial stages. Corrosion can also be problematic in later stages of compression for very wet gases, or when condensate is formed from process upsets, shut downs and startups that allow cooling of gas below its dew point in a given stage of compression.
One method of preventing corrosion of metal components in gas compression equipment may be to construct such metal components using an alloy that is more resistant to corrosion. However, such alloys may be expensive. Thus, there is a need for a less expensive method for reducing corrosion in gas compression equipment.